Confused about antenna design

Having scanned through this thread, I must say the simplest solution has been overlooked. The cheapo antenna shipped with the SDR isn’t bad at all, it just needs to be trimmed to length and a groundplane added.

Trim it so it stands 2.9" tall (2.7" plus a little more since the whip doesn’t extend to the bottom).

Add some groundplane, like the steel lid off a gallon pain can. The bottom of the antenna is a tiny groundplane, it will couple into a bigger one.

That’s it. You’ll get much better performance than you did before. Put everything high up in the attic, wifi to get to internet, and you’re all set. No cables to run, no lengthy construction projects.

Stock antenna connected to only center wire of coax without any connection to groundplane (aluminium cap with glued magnet) on the bottom.

Stock antenna connected to only center wire of coax without any connection to groundplane (aluminium cap with glued magnet) on the bottom.

Not on mine. Shield was nicely spread out, and crimped in position by the press fit aluminum cap. I’m getting excellent results now, 60,000 position reports in a day, and >1200 aircraft seen. Noticeable improvement just by clipping to proper length, and putting on paint can lid.

a little side question about antennas.

What compound is better/best for sealing exterior antenna terminals (weatherproofing it)
i.e non-corosive silicon, acryl baed sealant, polyuretanne based sealant, bitum based sealant

For sealing terminals connectors (N or the SMA or F connectors) I would suggest amalgamating or “self fusing tape”. This would allow you to remove the connectors later and they seal great. Just a few layers of tape can probably seal for a decade and very easy to remove later.

Professional will use layers of different sealant for more permanent connections. IE. Self fusing tape + electronic tape + connector goop + more tape. These connectors can last a few decades and usually overkill and quite hard to remove.

For sealing other parts of the antenna (the gaps on the antenna enclosure or between antenna sections) depends also on how long you want it to last. Usually an epoxy made for outside will work best (this is what is used on the FA antenna). Anything rated for outside is good like silicon, polyuretanne, etc. Also hot glue actually works quite well too but might melt in warmer temperatures.

You have to remember that water can enter through the antenna and then into the cable. Keeping the antenna waterproof is a very good idea.

Connectors are usually self sealing between the threads. If you make connectors tight enough they are water proof.

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hello david, i am not sure of the rules of this forum. are we allowed to post a link to a company that sells a nice waterproofing kit for antennas and connectors?

Thanks David,
it is for encapsulating balloon and feeder connection to vibrator

I think UV resistant polyurethane will fit. Epoxy is good but very hard and not elastic. It is ideal for gaps and antenna enclosures i.e. tube or so.

Try this:

  1. Self amalgamating tape (Scotch 2242 or 3M 215 Temflex);
  2. Follow this with a layer of Scotch 33+. The 33+ is required for UV resistance.
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i use a product from DX Engineering called “weather proofing kit” the part number is DXE-WK-1. it contains both amalgamating tape and heavy duty black tape and nice instructions.

I water-proofed my antenna by placing it inside my apartment…benefit of HOA not allowing any antenna outdoors. :rofl: :wink:

Having done so many antennas i’m astonished you have never built one of those directional antennas with the parrallel metal bars :wink:

Yagi-Uda you mean?

Usually just a bit of generic self-fusing tape would work fine. 3m definitely makes some of the best stuff for professional antenna installers. We can’t have cellphone towers from losing connections :slight_smile:

There are some installs that went very low tech with 2 liter soda bottles. I always wanted a gallery for ADSB sites. There is an amazing amount of variations out there and you can see that you don’t need to use the recommended things but whatever you have local and easy to get.

hello david, i am not sure of the rules of this forum. are we allowed to post a link to a company that sells a nice waterproofing kit for antennas and connectors?

I don’t have a problem with people linking to products that are in line with the thread. Spamming products that don’t have to do with antenna sealing is bad.


ADSB signals are vertical polarized. TV signals are horizontally polarized and the metal bars are in the horizontal direction.

Definitely make sure your antenna has the correct orientation for ADSB.

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A Yagi can be vertically polarized as well, the ‘problem’ is, whether vertical or horizontally polarized, it’s directional.

Unless one is focusing on a particular direction, the Yagi is not a good option for ADS-B.

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This is my case. I want 360° coverage, but even the best omnidirectional antenna cannot get me that - I am surrounded by high-rise buildings, and my antenna sees aircrafts visible in the slots between buildings. What I need is an x-ray antenna which can see through the buildings. :slightly_smiling_face:

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Here are some directional antennas with parallel metal bars :rofl:






1 - Directional antennas

2 - Directional antenna

3 - yagi - do you have experience with directional antennas?

4 - 1090 Mhz beam antenna

Agree. Anything will fit with good adhesion UV resistance and no acid involved. As for hot silicone I noticed that the one I tried is easily detached from the base once hardened.Self-fusing tape is great for connectors and here also could fit but in this particular case I should remove all the black plastic which is not good idea as it is involved in mechanical construction of the antenna. Rather I will use it as base and will fill up with kind of compound, most likely UV resistant polyurethane. Afterwards may insure it with selfamalgamating tape as suggested.
Will share result here.

That actually is one reason I decided aigainstputting it outside, as it meant to place it somewhere I could not easily reach and check if something is wrong due eg water ingress.